XRT Picture of the Week (XPOW)

It's not often that XRT sees bright, long, linear structures like the one on the left
side of the red image above, just below the center. That's because XRT detects plasma
at several million degrees, which is generally confined to the bent, non-potential magnetic field lines
energetic enough to do the heating. X-ray jets and
emission associated with current sheets are linear features
that XRT might detect, but we don't see the bursty flow of a jet in the AIA 94 Å images
above (green) and this is probably too thick to be related to a current sheet.
The faintness of the feature at 94 Å, and the complete lack of emission in
any of the other AIA channels, also tells us that it's at the hotter end of
XRT's temperature response,
around 10 million Kelvin. Some insight may be gleaned from the potential field source
surface
(PFSS) model,
which extrapolates the coronal
potential field based on
measurements of the surface magnetic flux.
The model predicts a field line (really a bundle of field lines) that's almost perfectly aligned
with the XRT feature, highlighted by the thick white line in the upper right image.
This field line connects a fan structure, completely invisible to XRT,
to a region near the small brightening that occurs in the far left of the AIA/94 movie.
Perhaps then, the small flare that produced the brightening also injected enough hot
plasma for the line to be seen by XRT, which is a prosaic explanation for this unusual observation.
(Also note the beautiful "X" configuration between the two active regions at disk center.)